Forces and Motion — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. A bigger push on a toy car makes it move with more speed.
In Grade 3, a larger force on the same object gives it more speed along the same direction.
2. Two friends pushing a box in the same direction make it move faster.
In Grade 3 science, pushes in the same direction add, so the box speeds up more than with one pusher.
3. Two equal pushes in opposite directions cancel each other out.
In Grade 3, equal and opposite forces cancel, so the object stays still or keeps the same motion.
4. If you double the push on a cart, its speed will double.
In Grade 3 science, doubling the push roughly doubles the speed change for the same cart.
5. A push is one kind of force that can change motion.
In Grade 3, a force is any push or pull, and pushes are one kind of force that change motion.
6. When forces on an object are equal and opposite, we say they are balanced.
In Grade 3 science, balanced forces add to zero, so the object does not change its motion.
7. When the total force is not zero, we say the forces are unbalanced.
In Grade 3, unbalanced forces cause a change in motion, like speeding up or changing direction.
8. If two kids pull on a rope with equal force, the rope does not move.
In Grade 3 science, equal pulls in opposite directions are balanced, so the rope stays in place.
9. Pushing a swing at just the right time makes it swing higher.
In Grade 3, a push in the same direction as the swing's motion adds energy, so it goes higher.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
Two equal pushes in opposite directions
→ Forces cancel and the object does not move
Forces cancel and the object does not move
Two pushes in the same direction
→ Forces add and the object speeds up
Forces add and the object speeds up
Doubling the push on a cart
→ Speed about doubles
Speed about doubles
One strong pull with no other force
→ Unbalanced force makes the object move
Unbalanced force makes the object move
In Grade 3, opposite equal pushes cancel, same-direction pushes add, doubling force doubles speed, and one pull is an unbalanced force.